DETROIT (Reuters) - The Chevrolet Spark all-electric subcompact car will cost U.S. buyers as much as 38 percent less than what it takes to buy its larger sibling, the hybrid Volt, General Motors Co said on Thursday.

The 2014 Spark EV, which goes on sale next month in California and Oregon, will sell for as low as $19,995 after accounting for the full federal tax credit of $7,500, GM said. The larger Chevy Volt, which was introduced in the fall of 2010, sells for about $32,500 after the tax credit.

"The Chevrolet Spark EV is the most efficient - and now one of the most affordable - EVs you can buy," Chris Perry, GM's vice president of Chevrolet marketing, said in a statement.

GM has made rolling out cars with electrical technology -- including its eAssist system that boosts fuel efficiency in gasoline-powered cars -- as a central part of its global strategy.

The U.S. automaker is aiming by 2017 to build up to 500,000 vehicles a year that include some form of electric engine power, including cars like the Spark EV, the Volt and those with eAssist. GM will begin building the Cadillac ELR plug-in electric coupe late this year.

The rollout of the Spark EV continues GM's push to seize the mantle of "greenest automaker in the world" from Toyota Motor Corp., which makes the popular Prius hybrid car. Toyota also sells a plug-in version of the Prius.

California Spark EV owners also could qualify for an additional $2,500 in state tax credits and incentives, GM said. The car will lease for as low as $199 a month for 36 months with $999 due at signing.

GM previously said the Spark EV will be able to travel twice as far on an electric charge as the plug-in hybrid Volt can go before its gas engine kicks in.

The Spark EV has a combined city/highway range of 82 miles when fully charged as estimated by the U.S. Environmental Protection Agency. The Volt gets about 40 miles on an electric charge. The Spark EV's fuel economy is equivalent to 119 miles per gallon on an EPA-estimated combined city/highway basis.